The present invention relates to a method and apparatus for sharpening an image.
The invention has been developed primarily for a digital camera including an integral printer for providing a paper print of an image captured by the camera and will be described hereinafter with reference to that application. However, it will be appreciated that the invention is not limited to that particular field of use.
According to a first aspect of the invention there is provided a method for sharpening an image, the method including the steps of:
receiving a data set indicative of the image; extracting an initial luminance channel from the data set;
sharpening the initial luminance channel to form a revised luminance channel; and
incorporating the revised luminance channel into the data set.
Preferably, the extracting includes the step of deriving the initial luminance channel from the data set.
More preferably, the data set has a red plane, a green plane and a blue plane and the method includes the step of deriving the initial luminance channel from the planes.
Even more preferably, the data set includes the initial luminance channel as a separate channel and the extracting includes the step of accessing the initial luminance channel. Preferably also, the sharpening includes the further steps of:
high-pass filtering the initial luminance channel to provide a filtered luminance channel; and
forming the revised luminance channel from the sum of the initial luminance channel and a predetermined proportion of the filtered luminance channel.
In a preferred form, the high-pass filtering utilises a 3xc3x973 convolution kernel. In alternative embodiments, however, the high-pass filtering utilises a 5xc3x975 convolution kernel. In further alternative embodiments the high-pass filtering utilises a 7xc3x977 convolution kernel.
According to a second aspect of the invention there is provided an apparatus for sharpening an image, the apparatus including:
input means for receiving a data set indicative of the image;
extraction means for extracting an initial luminance channel from the data set;
sharpening means for sharpening the initial luminance channel to form a revised luminance channel; and
processing means for incorporating the revised luminance channel into the data set.
Preferably, the extraction means derives the initial luminance channel from the data set. More preferably, the data set has a red plane, a green plane and a blue plane and the extraction means derives the initial luminance channel from the planes.
Preferably also, the data set includes the initial luminance channel as a separate channel and the extraction means accesses the initial luminance channel.
In a preferred form, the sharpening means:
high-pass filters the initial luminance channel to provide a filtered luminance channel; and
forms the revised luminance channel from the sum of the initial luminance channel and a predetermined proportion of the filtered luminance channel.